The design of a conventional chassis for a motor vehicle represents a compromise between driving safety and driving comfort, since a hard damping guarantees good handling and a soft damping increases comfort. In order to be able to combine both aspects, active chasses for compensating for shaking, pitching and piston stroke movements are known from the state of the art.
A spring-shock absorber device for a motor vehicle is known from German Patent 196 06 991 A1 in which the separation of the vehicle body from the wheels can be controlled by a hydraulic unit according to the driving behavior of the vehicle, whereby the spring is clamped between a moving element of the hydraulic unit and a damping cylinder of the shock absorber, and the moving element of the hydraulic unit is placed in a sliding manner on the shock absorber such that the displacement only occurs in the area of the piston rod of the shock absorber, whereupon the friction forces are largely reduced during the displacement of the moving element.
A piston-cylinder unit is also known form German Patent 196 04 558 C1 and includes a cylinder in which a piston rod is positioned to move axially, a first connection device in an active connection with the cylinder; a second connection device, which is connected with the piston rod; a positioning cylinder with a pressure medium connection, whereby the positioning cylinder is in an operative connection with one of the connection device and by means of adding or removing the pressure medium, the separation between the first and the second connection devices can be adjusted. In the process the positioning cylinder is placed in series with the cylinder and the piston rod represents a guide track for the positioning cylinder.
In addition, an adjustable spring strut for motor vehicles is known from German Patent 195 29 580 A1, which enables a good position control of the spring-loaded vehicle parts and is supposed to manifest a defined, controllable, and tunable damping and cushioning rate. The spring strut includes a vibration damper surrounded by a coil spring with a damping cylinder, whereby the coil spring is so held and tensioned, on the one hand, by an initial spring plate connected by an external and an internal positioning cylinder concentrically surrounding the damping cylinder and, on the other hand, by a second spring plate connected with the piston rod in the vicinity of the articulation point of the piston rod of the operating piston so that when the piston is withdrawn into the damping cylinder the coil spring is tensioned. In the process, the two positioning cylinders to change the ground clearance of the car body are constructed so as to move in a telescoping manner in relation to each other.
In the construction known from German Patent 195 29 580 A1, the first spring plate is secured to the external positioning cylinder, whereby the external positioning cylinder manifests on its end facing the piston rod devices to guide and seal the damping cylinder and on the opposite end devices to guide and seal the internal positioning cylinder. In the process, the internal positioning cylinder is secured to the damping cylinder and displaces in a telescope manner relative to the external positioning cylinder by the introduction of a pressure medium into the ring-shaped, interior space bounded by the positioning cylinders and the damping cylinder.
In the framework of German Patent 100 43 711 A1, an actuator for active vehicle chassis control is described using a positioning member that produces a torque, which is connected with guides on the wheel and on the vehicle body, whereby the positioning device is placed between the vehicle body and the guides and conveys a torque to the guides corresponding to the shaking and pitch compensation and/or a torque guaranteeing the damping of the guide oscillations. The positioning device is preferably constructed as a swivel motor.
Another actuator for active vehicle chassis control is known from German Patent 103 06 228 A1. It includes a positioning device placed between the wheel and the vehicle body which compensates for pitch and shaking movements and also reduces the piston stroke movements according to the skyhook principle. The positioning device is constructed as a swivel motor and also, between the wheel and the vehicle body, makes an actuation moment available to reduce the body piston stroke movements in addition to an actuation moment for the shaking and pitch compensation.
The energy requirement for the constructions known from the state of technology is disadvantageously high because of the displacement of the base of the suspension system and the activation of the actuator.
This invention is based upon the objective of providing an actuator for an active chassis to influence the pitch, piston stroke and shaking movements for active chassis control, whose energy requirement is slight in comparison to systems known from the state of technology.